Long-term outcomes of two ablation techniques for treatment of radio-recurrent prostate cancer

Background: In men with recurrence of prostate cancer post radiation therapy, further treatment remains a challenge. The default salvage option of androgen-deprivation therapy (ADT) has adverse effects. Alternatively, selected men may be offered salvage therapy to the prostate. Herein, we present long-term oncological outcomes of two whole-gland ablation techniques, cryotherapy (sCT) and high-intensity-focused ultrasound (sHIFU). Methods: Men undergoing sCT (1995–2004) and sHIFU (2006–2018) at Western University were identified. Oncological endpoints included biochemical recurrence (BCR), ADT initiation, metastases, castration resistance (CRPC), and prostate cancer-specific mortality (PCSM). Survival analysis with competing risks of mortality was performed. Multivariable analysis was performed using Fine and Gray regression. Results: A total of 187 men underwent sCT and 113 sHIFU. Mean (SD) age of the entire cohort was 69.9 (5.9 years), median pre-radiation PSA 9.6 ng/ml (IQR 6.1–15.2), and pre-salvage PSA 4.5 ng/ml (IQR 2.8–7.0). Median total follow-up was 116 months (IQR 67.5–173.8). A total of 170 (57.6%) developed BCR, 68 (23.4%) metastases, 143 (49.3%) were started on ADT, 58 (20.1%) developed CRPC, and 162 (56%) patients died of which 59 (36.4%) were of prostate cancer. On multivariable analysis, sHIFU (HR 1.65, 95% CI 1.15–2.36, p = 0.006) and pre-salvage PSA (HR 1.09, 95% CI 1.06–1.13, p < 0.0001) were associated with a higher risk of BCR. Similarly, sHIFU patients had a higher risk of CRPC (HR 2.31, 95% CI 1.23–4.35, p = 0.009). The cumulative incidence (for both treatments) of PCSM was 16.5% (95% CI 12.2–21.4%) at 10 years and 28.4% (95% CI 22.1–34.9%) at 20 years, with no difference between treatment modalities. Pre-salvage PSA was a common predictor for the measured oncological outcomes. Conclusions: Although sHIFU had higher BCR and CRPC rates, there were no differences in PCSM when compared with sCT. The long-term oncological data on two ablation techniques highlighted that only 50% of patients started ADT after 10-year follow-up.